Gardeners apply a wetting agent, sometimes called a soil wetter, to the garden to make sure that the water from the sprinklers and the rain soaks right down into the soil.
Over time, the soil in the garden or in pots becomes ‘hydrophobic‘ which means that the water won’t soak into it. If this happens, the water just sits on the top and doesn’t get deep down where the roots of plants of plants are. This might cause them to die or not thrive. Applying a wetting agent to the soil stops this problem and makes sure that our precious water is not wasted.
There are many brands of wetting agents. Some are granules which are scattered over the soil and pots and then watered in and others are a liquid and are mixed with water before applying to the garden.
They all work in just about the same way. They break up the invisible waxy coating that is on the soil that stops the water from soaking in so that next time the sprinklers are on or the rain comes, all of the water gets down to the plant’s roots.
It’s important to apply a wetting agent to the garden, including the lawn, or pots at least twice a year as the waxy coating will come back again which means the water will be wasted and the plants will struggle.
Here in WA, gardeners have to contend with arguably the most impoverished and non-wetting soils in the world. We trudge along, constantly topping up mulch, adding clay and applying wetting agents. Many of us grumble - it seems unfair to have to go to so much effort to have a flourishing garden - but view it as the price we have to pay for our near perfect weather for 9 months of the year. Due to our water repellent soils, wetting agents are widely used in Perth and their use is pretty much essential if we wish to maintain a healthy garden. WHAT IS NON WETTING SOIL? If you are watering a plant and it puddles in the centre of the plant, or the water runs off to the side rather than down into the soil, you have non wetting soil. If your plants look sick or have died, the first port of call should be to check the soil wettability. Soil wetters, both liquid and granular; work by improving the absorption of water, reducing the surface tension of water and helping it to spread more evenly through the soil profile. However not all wetting agents are created equal.
Here at Garden Deva, we have found liquid wetting agents to be the most effective. Lawn seems to be happy with either granule or liquid wetting agent.
Many people are unaware that the granular wetting agents must be kept wet to remain active. If the granules and the soil with which they are in contact dries out for a week or more, they become a lot less active and are rendered ineffective.
Conventional wetting agents include synthetic compounds such as petrol distillates like polyacrylamides as well as alcohol. Conversely, natural surfactants in (Certified) organic wetting agents utilise soaps, saponins, microbial agents, and organic humectants.
Most soil wetters, as well as kitchen or laundry detergents; will strip soils of goodies, kill earthworms and upset the soil biota. This is bad news for your plants and soil.
To help choose a suitable wetting agent simply check the ingredients. Look for soil conditioners like fulvic acid and seaweed, polysaccharides (natural humectants which draw moisture from the air), and natural soil surfactants (potassium soaps and saponins). These will add rather than detract from your soil.
At the time of writing this article, we have found that the only wetting agents which actually work and also improve soil microbial activity are liquids Eco Hydrate, from Organic Crop Protectants and Eco Wet from Eco Growth.
Eco hydrate contains humates and organic polymers which assist in moisture penetration and improve soil structure. It comes in a 1L container which will cover 330 sqm. You will need 3-4 capfuls per 9L watering can. For a small to average sized garden, you will usually only need one bottle per year.
Eco wet is similar in content to Eco hydrate but it is locally produced in WA. 1L will treat up to 200m2.
(Please note, GARDEN DEVA receives no remuneration for endorsing any product).
We believe that the most effective time to apply a wetting agent in Perth is in September or October and again in December or January. Apply the liquid wetting agent with a watering can, then water it in again with a hose to ensure excellent penetration. It will froth up both in the watering can and on the ground. Some gardeners like to give their soil another application in winter when it is raining.
OTHER STRATEGIES FOR SANDY SOILS.
When planting in sandy soil, it is essential to incorporate a clay amendment. These include: Sand to Soil, Soil Solver, Sand remedy and Watheroo clay. Clay based amendments make the soil more friable and help to hold on to both moisture and fertiliser, thereby saving you money and preventing our precious rivers from excess nitrogen pollution which causes algal bloom.
It goes without saying that our nutrient depleted soils need soil conditioning. Usually a ratio of between 30 and 50% soil conditioner to 70-50% soil is recommended; the amount varying depending on the quality of your soil. Soil improver may be bought in bags from garden centres or you may use your own compost or worm castings. Manure is also often added to the planting hole but we prefer to add this to the compost bin and utilise as mature compost when it’s ready.
Always thoroughly mix soil conditioner and clay amendments with the existing soil, using water to achieve a chocolate-y loam texture. Never plant straight into a hole with unmixed soil conditioner or compost. Your plant roots will burn and most likely it won’t be long before the plant dies. Other soil amendments may include kelp powder, charcoal and rock dust minerals.
Always mulch your garden. In cooler weather, keep mulch to a minimum, say 20-30mm depth. This helps to ensure adequate rain penetration in winter when your reticulation is turned off in winter. (There is a sprinkler ban in WA from June 1 – August 31st each year).
Some gardeners are surprised when they clear away their mulch after winter and discover an ailing plant which is dry due to too thick a coverage. However in summer, after applying your preferred wetting agent and ensuring your reticulation is working well, aim to have between 50-70mm for your mulch depth.
Chemical wetting agents are often used in potting mixes which is usually not the end of the world but be aware that some soil wetters can damage sensitive plants like ferns, orchids and members of the protea family (including hakeas, banksias, grevilleas and leucodendrons).
If possible, choose potting mixes containing coir peat, which is itself a moisture retentive medium.
HOW DO I KNOW IF MY POT HAS DRIED OUT?
Simply insert a dry finger deeply into the mix and you will soon feel the lack of moisture. Another indicator is that the pot will feel light to pick up or water seems to run out of the base of the pot suspiciously quickly when you water.
To remedy this, simply immerse the pot in a bucket of weak seaweed liquid (another mild soil wetter), to which you have added a liquid wetting agent. Remove the pot when the bubbles stop. In some cases, you may need to repot the plant as it may be pot bound. Take the plant out of the pot and have a look at the roots to see if you need to repot.
WATER SAVING CRYSTALS are another option for potted plants but the jury is still out on the effect of these on soil microbes and roots. Just to be sure, avoid using them with edibles. Always mix crystals in a bucket with water and add to the potting mix rather than adding dry and watering. You will find if you do the latter, the jelly like crystals will often spill over the edge of your pot.
COPYRIGHT GARDEN DEVA JUNE 2017
Jerry uses a range of techniques to prevent his soil from becoming hydrophobic and repelling water during periods of dry weather, focusing on soil improvement.
Succession Mulching
Using the principles of succession mulching, Jerry initially added aged mushroom compost to the soil, followed a season later with a topping of pine bark mulch, then tea tree mulch the following season. The current mulch layer is a straw-based mulch of sugar cane. Each of the mulches Jerry utilises favours a different group of soil microorganisms, and over the years of succession mulching, these microbes have built up to allow the soil to accept the rainwater when it falls.
Both pine bark and eucalypt bark mulches are fantastic in the garden and have many applications, but it is important to remember that they may become counter-productive over time, given their relationship with some soil-borne fungi. If used over long periods of time, the mulch and fungi can bond and form plates, preventing the deep penetration of water and oxygen.
Wetting Agents
While there are many soil additives and wetting agents commercially available, it has been shown that these don’t biodegrade readily in the soil and can cause issues with sensitive animals and plants (including members of the Proteaceae family and animals such as lizards). To combat this, Jerry makes his own wetting agent from readily available food grade agar, a gelatine made from seaweed.
Method
- Dissolve agar in warm water (not hot) to dilute to consistency of runny custard
- Take 2 cups of this dilution and add to 9 litres of water (a watering can is ideal)
- Apply with a watering can - this will treat 6 sqm of soil.
Watering the soil before you are going to add the wetting agent will aid both the dispersal and effectiveness of the wetting agent. You can expect the effects of this application to last around three weeks, which while shorter than the commercially available products, means that it is readily biodegradable and far kinder to the soil. It is also the perfect amount of time for a tender young seedling to establish during the warmer months.